The process of organ transplantation has been revolutionized since the first successful kidney transplant in identical twins more than five decades ago (Harrison et al., Surg. Forum 6:432-436, 1956; Merrill et al., J. Am. Med. Assoc. 160:277-282, 1956). Since then, the use of immunosuppressants, such as cyclosporine, have improved the outcome of transplants (Calne, Mt. Sinai J. Med. 54:465-466, 1987), but the process is still fraught with many challenges, such as the management of chronic and acute rejection, nephrotoxicity from immunosuppressant and antiviral drugs, and avoiding reactivated (or novel) infectious agents that could threaten the graft. To balance these needs, clinical guidelines on the management of kidney transplant (Kasiske et al., Am. J. Transpl. 9:S1-S155, 2009) generally suggest the use of an immunosuppressant and an anti-proliferative agent in the initial stages of the process, followed by a lowering of dose of immunosuppressants if there is no acute rejection. However, careful monitoring of allograft function is crucial; and tests to detect increase in proteinuria, elevated serum creatinine levels, and detection of viral nucleic acids in plasma are also recommended.
One of the problems that threatens kidney allograft survival is the development of polyomavirus-associated nephropathy (PVAN) (Purighalla et al., Am. J. Kidney Dis. 26:671-673, 1995; also known as BKV associated nephropathy (BKVN)). Left untreated, PVAN can lead to a loss of the allograft, but early diagnosis, monitoring and intervention can prevent it. In kidney transplant recipients, current estimates of PVAN are about 1-10% (Ramos et al., Clin. Transpl. 2002:143-153; Hirsch et al., Transplantation 79:1277-1286, 2005), and graft losses range from 10-100% (Hirsch and Steiger, Lancet Inf. Dis. 3:611-623, 2003) depending on the drug regimen, monitoring, and interventions performed. Polyomavirus-associated pathologies such as PVAN or progressive multifocal leukoencephalopathy (PML) also cause significant morbidity or even mortality in other patients receiving immunosuppressive therapy (for example, for auto-immune disorders).